Photooxidation of dimethyl sulfide (DMS) in air in the presence of NO was studied. Sulfur dioxide (SO2) and methanesulfonic acid (CH3SO3H) are major sulfur-containing products. In the reaction systems of DMS-NO-air with low initial NO concentration and DMS-CH3ONO-air, in which OH radical-initiated photooxidation prevails, the yield of SO2 was determined to be 20.7¿1.2%. The yield of methanesulfonic acid is more than 5% of the consumed DMS. Sulfuric acid was also detected as a minor product with a yield of less than 2%. The implications of these results on the atmospheric sulfur cycle are discussed.